Fix arguments passed to predict function in QA Seq2seq training script

[Observer46]

What does this PR do?

I used the script for training Seq2seq QA and realized that --do_predict contains a bug - kwarg outputs should be an instance of class EvalLoopOutput, but NumPy array is passed instead. Together with extracting predictions in the body of the method post_processing_function (line 610 in run_seq2seq_qa.py) this results in an error every time you try to run tests with this script.

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Who can review?

@karthikrangasai @sgugger

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[sgugger]

Thanks for the fix!